> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Robert Rolf

> That current sure is high. Typical spec is under 2uA.
> What current is your battery voltage divider drawing?
> To minimize that current you need to switch it out
> somehow (P chan VFET with OC pin driving gate that pulls up to vbatt).
>
I think that's the solution.  The voltage divider will draw about 50uA at 6V
if I did the calculation right.  So with 50uA for the regulator and 5uA from
the op amp, that pretty much explains it.

I knew it was drawing somthing, but was hoping there was some way to isolate
the pins internally.  But I guess it needs to be switched back to vbat as
you say.

Or maybe I could use bigger resistors....?

> Are your outputs pulling against any pullups? If so, you have to make
> the pin the same level as the pullup when you sleep.

No

> What current do you get when you have the PIC alone, not connected to
> anything else but it's crystal (but with inputs terminated)?
> How are you waking it up? Is there a current path there? Could you
> get away with shutting the whole thing off an thereby dump your
> regulator current too?
>

There is no crystal.  Its running on internal rc with io.

> What crystal frequency are you using? And you're sure it's off?

Yes.  I turned the clkout on temporarily just to check that.

> What VCC?

4V from the regulator

> What about board leakage due to wrong choice of flux/failure to clean?
> I have found that some 'no clean' fluxes are quite resistive in fact.
> If you want the lowest possible leakage, make sure you clean the board
> thoroughly and then conformal coat it.
>
I think thats ok.


> As for the analog pins, leaving them as input is fine, assuming the PIC
> still has VCC>. Switch the multiplexer to an unused channel to remove
> any possible leakage through the pin.

Ahhhh.  I will do try that too!


Thanks for your response.

Bruce
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